The common clinical causes of black ankles are as follows: a. Patients with severe varicose veins in the lower limbs, due to local blood stagnation can cause skin ischemia and hypoxia changes, skin rupture or pigmentation, once infection occurs, the skin at the ankle can be blackened, at this time, patients need to give potassium permanganate solution to soak the skin at the ankle, control the infection and then perform high ligation of the saphenous vein plus segmental stripping. Patients with lower limb artery occlusion can have black color change due to severe ischemia and hypoxia of the muscle tissue at the ankle.